1. Technical Field
Embodiments of the invention relate to a management system for semiconductor manufacturing equipment. More particularly, embodiments of the invention relate to a management system for semiconductor manufacturing equipment capable of real-time monitoring the transfer of wafers between various pieces of semiconductor manufacturing equipment.
This application claims priority to Korean Patent Application No. 10-2005-0100156 filed Oct. 24, 2005, the subject matter of which is hereby incorporated by reference in its entirety.
2. Discussion of Related Art
The manufacture of semiconductor devices on silicon wafers generally involves a complex sequence of fabrication processes. Specific fabrication processes include, for example, deposition processes adapted to form material layers on a semiconductor substrate, photolithography and etching processes adapted to pattern the material layers, implantation processes adapted to selectively implant impurity ions, and various heat treatment processes.
Many of these fabrication processes are performed, in whole or in part, by highly automated systems that make use of custom processing equipment (e.g., process chambers) and work stations. All or much of the manufacturing process is typically accomplished in a large production facility. Accordingly, the physical transfer (e.g., process flow, holding and storage, etc.) of the silicon wafers through the production facility—in order to receive application of the proper sequence of processes—is a very complex engineering endeavor. It requires careful design and layout of the production facility and careful use of management tools. Indeed, the inevitable breakdown or maintenance down-time associated with a single piece of fabrication equipment may result in lengthy production lags for numerous wafers, unless the breakdown is quickly identified and remedied.
However, the largely automated nature of the production facility's equipment and the vast area occupied by this equipment in huge factory facilities make it difficult to effectively monitor the progress of various silicon wafers through the manufacturing process. As a result, numerous human operators are routinely hired to monitor and maintain the fabrication equipment in order to minimize production interruptions.
This large scale human interaction is often accomplished in relation to “lots” of silicon wafers. A wafer lot is a collection of wafers held in a single carrying apparatus referred to as a “wafer cassette.” Each wafer cassette holds a plurality of wafers intended to receive the same sequence of fabrication processes. Each wafer lot is associated with a barcode attached to the wafer cassette.
As a wafer cassette moves through the manufacturing process, its barcode is read by barcode readers associated with respective pieces of semiconductor manufacturing equipment. For example, the barcode for a wafer lot is read when the wafer cassette is loaded onto a piece of semiconductor manufacturing equipment. An indication is then made in a record or control process associated with the barcode that the constituent process performed by the equipment has been applied to the wafers in the lot.
A controller and/or a host computer may be used to accumulate processing information for various wafer lots as they pass through the manufacturing facility. If information regarding the processing state of a wafer lot is required, a human operator may query the host computer from a networked workstation (e.g., a Personal Computer).
This type of management approach allows data visibility down to the wafer lot level and the wafer cassette level. That is, the wafer lot in the conventional management system forms the basic unit of data granularity, as a cassette is transferred between numerous pieces of semiconductor manufacturing equipment.
However, this type of wafer management system suffers from several problems. For example, the process contains both automated and non-automated (e.g., human controlled) process steps. Thus, centralized optimization of the overall process is impossible as no control, and little visibility is possible over the non-automated process steps. As a result, the transfer efficiency and speed for wafer cassettes between different pieces of semiconductor manufacturing equipment are impossible to optimize.
Additionally, while the arrival and departure of cassettes may be tracked in point by point fashion, the conventional system offers no real-time mechanism for tracking actual movement (or lack of movement) by cassettes through the manufacturing process. Hence, production bottlenecks may not be identified in real-time.
Additionally, information regarding a particular cassette may only be determined when an operator reads out the information at a test station using (e.g.) a barcode reader. This approach can require a great deal of time and precludes a real-time understanding of a particular wafer's processing status. All of these problems adversely effect productivity.